Implementing with-items concurrency

* It allows executor to run at most N actions
   related to current with-items task at a time.

Implements blueprint: with-items-concurrency
Related-Bug: #1476871
Related-Bug: #1484483

Change-Id: Ifb193f06ae8e9becb6c43f36c07f5ffddb04c71c

mistral/tests/unit/workflow/test_with_items.py

@@ -0,0 +1,55 @@
+# Copyright 2015 - Mirantis, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License");
+#    you may not use this file except in compliance with the License.
+#    You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS,
+#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#    See the License for the specific language governing permissions and
+#    limitations under the License.
+
+
+from mistral.db.v2.sqlalchemy import models
+from mistral.tests import base
+from mistral.workflow import states
+from mistral.workflow import with_items
+
+
+class WithItemsTest(base.BaseTest):
+    @staticmethod
+    def get_action_ex(accepted, state, index):
+        return models.ActionExecution(
+            accepted=accepted,
+            state=state,
+            runtime_context={
+                'with_items_index': index
+            }
+        )
+
+    def test_get_indices(self):
+        # Task execution for running 6 items with concurrency=3.
+        task_ex = models.TaskExecution(
+            runtime_context={
+                'with_items_context': {
+                    'capacity': 3,
+                    'count': 6
+                }
+            },
+            executions=[]
+        )
+
+        # Set 3 items: 2 success and 1 error unaccepted.
+        task_ex.executions += [
+            self.get_action_ex(True, states.SUCCESS, 0),
+            self.get_action_ex(True, states.SUCCESS, 1),
+            self.get_action_ex(False, states.ERROR, 2)
+        ]
+
+        # Then call get_indices and expect [2, 3, 4].
+        indices = with_items.get_indices_for_loop(task_ex)
+
+        self.assertListEqual([2, 3, 4], indices)